The present invention relates to a non-catalytic method for reducing the concentration of NO in combustion effluents by the injection of ammonia into the effluent stream the apparatus for carrying out the injection. In particular, the present invention is directed to the reduction of NO in combustion effluents produced by incineration of absorber off gas streams found in chemical plants such as in acrylonitrile plants by the injection of ammonia into the effluents stream at a temperature below 1375.degree. F.
Combustion effluents and waste products from various installations are a major source of air pollution when discharged into the atmosphere. One particular troublesome pollutant found in many combustion effluents streams is NO.sub.2, a major irritant in smog. Furthermore, it is believed that NO.sub.2 in the presence of sunlight and hydrocarbons undergoes a series of reactions known as photochemical smog formation. The major source of NO.sub.2 is NO which to a large degree is generated at such stationery installations such as gas and oil fired steam boilers for electric power plants, process heaters, incinerators, coal fired utility boilers, glass furnaces, cement kilns, and oil field steamed generators.
Various methods have been developed for reducing the concentration of nitrogen oxides in combustion effluents. One such method which has been developed was a non-catalytic thermal deNO.sub.x method discloced in U.S. Pat. No. 3,900,554 assigned to Exxon Research & Engineering Company. The process disclosed in the patent shows the reduction of NO.sub.2 by injecting ammonia into the combustion effluents stream. This basic procedure was subsequently further refined as set forth in U.S. Pat. Nos. 4,115,515, 4,507,269, 4,636,370 and 4,624,840 also assigned to Exxon. These patents are directed to non-catalytic method for reducing the concentration of NO in combustion effluents by (1) injection of ammonia into combustion effluents which are maintained at a high temperature or (2) injection ammonia into the combustion effluent at a location determined by solving a specific kinetic equation.
The present invention is directed to an improvement in these methods and a novel apparatus which allows for the injection of the ammonia at a substantially lower temperature than that utilized in these patents without the need for solving the complex kinetic equation.